A novel soil remediation technology for simultaneous heavy metals immobilization and nitrogen supplementation

Mining-related copper (Cu) and cadmium (Cd) contamination poses a serious threat to agricultural security and human health. To lessen the environmental danger of Cu and Cd in soil and improve soil environmental quality, we designed and prepared a soil amendment that could efficiently immobilize Cu and Cd in farmland and improve soil fertility. Sugarcane bagasse biochar was selected as the substrate, and nitrogen and magnesium oxide nanomaterials were doped on the biochar surface (denoted as Mg-N/BC) by a simple calcination method. After 90 days of incubation, the immobilization efficiencies of Cu and Cd were 64.3% and 45.2%, respectively, when the dosage of Mg-N/BC was 1%. Mg-N/BC increased soil pH, cation exchange capacity (CEC), and soil organic matter (OM), and facilitated the conversion of Cu and Cd ions from acid-soluble to more stable forms through ion exchange, precipitation, and complexation. Moreover, the urease and sucrase activities of the remediated soil increased by 60.14% and 301.2%, separately, reflecting the decreased toxicity of heavy metals to microorganisms. More importantly, Mg-N/BC immobilized soil heavy metals while supplementing nitrogen fertilizer in the soil, effectively promoting plant growth. This study provides a new strategy for simultaneous remediation of heavy metal-contaminated soil and improving soil fertility.